Dual walled titanium tubing and methods of manufacturing the tubing

Abstract

Within examples, a method of manufacturing a double-walled titanium conduit is described. Example methods include stitch welding multiple concentric sheets to form a stitch layer, providing the stitch layer between an inner wall and an outer wall of the double-walled titanium conduit, circumferentially seam welding the inner wall and the outer wall to the stitch layer to create a welded assembly, die forming the welded assembly at temperature and pressure to form inner structures between the multiple concentric sheets according to stitch welding lines and to enable a diffusion bond process among the inner wall, the stitch layer, and the outer wall, and removing the double-walled titanium conduit from the die.

What is claimed is: 
     
       1. A method of manufacturing a double-walled titanium conduit, comprising:
 stitch welding multiple sheets concentrically to form a stitch layer; 
 providing the stitch layer between an inner wall and an outer wall of the double-walled titanium conduit; 
 circumferentially seam welding the inner wall and the outer wall to the stitch layer to create a welded assembly; 
 die forming the welded assembly at a temperature and pressure to form inner structures between the multiple concentric sheets according to stitch welding lines and to enable a diffusion bond process among the inner wall, the stitch layer, and the outer wall; and 
 removing the double-walled titanium conduit from the die. 
 
     
     
       2. The method of  claim 1 , wherein the inner structures comprise at least one stiffener extending between the inner wall and the outer wall. 
     
     
       3. The method of  claim 1 , wherein stitch welding creates a pattern on the multiple sheets that form a size and shape of the inner structures. 
     
     
       4. The method of  claim 1 , wherein the double-walled titanium conduit is a tubular structure. 
     
     
       5. The method of  claim 1 , wherein the double-walled titanium conduit has an elliptical shape. 
     
     
       6. A method of manufacturing a double-walled tube, comprising:
 super plastically forming inner structures of the double-walled tube; and 
 diffusion bonding an outer wall, an inner wall, and the inner structures of the double-walled tube, the super plastically forming and diffusion bonding further comprising:
 arranging substantially intimately concentric seamless tubings; 
 stitch welding the seamless tubings with a rolled tubing seam welder to create a stitch layer including a stitch pattern; 
 circumferentially seam welding concentric outer sheets of the outer wall to the inner wall and the stitch layer to create a welded tube assembly; 
 inserting a cylinder die into the welded tube assembly; 
 placing the welded tube assembly into a heated die; 
 bringing the welded tube assembly up to temperature; 
 pressurizing the welded tube assembly to form the inner structures according to the stitch pattern; 
 holding pressure for a diffusion bond process between the outer wall and the inner wall; and 
 removing a resulting tube part from the heated die and cooling the resulting tube part. 
 
 
     
     
       7. The method of  claim 6 , wherein the concentric seamless tubings have approximately matching diameters to enable contact during stitch welding. 
     
     
       8. The method of  claim 6 , further comprising cleaning the seamless tubings to remove oxidation. 
     
     
       9. The method of  claim 6 , wherein stitch welding the seamless tubings comprises creating the stitch pattern along a length of the seamless tubings. 
     
     
       10. The method of  claim 6 , wherein circumferentially seam welding outer sheets of the outer wall to the inner wall and the stitch layer comprises:
 placing the inner wall between a first outer sheet and a second outer sheet; and 
 circumferentially welding a perimeter of ends of the first outer sheet, the second outer sheet, and the inner wall. 
 
     
     
       11. The method of  claim 6 , wherein placing the welded tube assembly into the heated die comprises placing the welded tube assembly into a lower die and an upper die. 
     
     
       12. The method of  claim 6 , wherein bringing the welded tube assembly up to temperature comprises heating the welded tube assembly to a temperature in the range of about 1450° F. to about 1850° F. 
     
     
       13. The method of  claim 6 , wherein pressurizing the welded tube assembly to form the inner structures comprises:
 causing the outer sheets to fill contours of the heated die; and 
 pressurizing the seamless tubings of the inner wall to form cells within the inner wall based on the stitch pattern. 
 
     
     
       14. The method of  claim 6 , wherein pressurizing the welded tube assembly to form the inner structures comprises pressurizing at a pressure of about 300 psi. 
     
     
       15. The method of  claim 6 , wherein holding pressure for the diffusion bond process between the outer wall and the inner wall comprises holding pressure for a time period to enable the outer wall and the inner wall to go through the diffusion bond process such that the outer wall and the inner wall become an integral piece. 
     
     
       16. The method of  claim 1 , wherein stitch welding the multiple sheets comprises creating a pattern along a length of the multiple sheets. 
     
     
       17. The method of  claim 1 , wherein die forming the welded assembly at the temperature and pressure to form inner structures between the multiple concentric sheets comprises:
 bringing the welded assembly up to a temperature in the range of about 1450° F. to about 1850° F. 
 
     
     
       18. The method of  claim 1 , wherein die forming the welded assembly at the temperature and pressure to form inner structures between the multiple concentric sheets comprises:
 pressurizing the welded assembly at a pressure of about 300 psi. 
 
     
     
       19. The method of  claim 1 , further comprising holding the pressure for the diffusion bond process between the inner wall, the stitch layer, and the outer wall for a time period to enable the outer wall and the inner wall to go through the diffusion bond process such that the outer wall and the inner wall become an integral piece. 
     
     
       20. The method of  claim 6 , wherein the double-walled tube is a double-walled titanium conduit.